Tuesday, 27 October 2009

Shampoo : SLS for 'clean' hair.

In the first post this week - we learned about micelles and how they are formed (click here if you haven't read it or want an introduction to micelles).

Today I am talking about SLS (sodium lauryl sulphate). It has this reputation as an extremely drying terrible ingredient. However, there is a reason why it is used in shampoo. It is an extremely good surfactant. Here are two scenarios to illustrate this.

Scenario 1 - Imagine washing your hair with just plain water.

From a chemical view point, scrubbing your hair and using warm water will help dislodge some oil, but really not that much (See the diagram below - remember you can click it to make it larger if you wish)

Scenario 2 - Washing your hair with SLS containing shampoo

When a surfactant such as SLS is used, oil can be dissolved away from the hair. The hair is left squeaky clean and oil free. This is because SLS can form micelles which help carry the oil away during the rinsing of the shampoo.

Now not everyone wants squeaky clean hair. Curly hair does pretty well with some oil on it. However if you are trying to get rid of a silicone product, have too much oil on your hair or have used a product that you didn't like and your conditioner isn't helping you, some SLS shampoo may actually work to give you a clean slate.

There are surfactants in conditioner (for example behentrimonium chloride) , but these are not nearly as comparable to SLS.

Tomorrow I'm going to have a break from the science and talk about my fave site BGLH but on Thursday I will be back with the next installment - Can mixing olive oil and coconut oil yield mixed micelles?! What do you think?


  1. thanks for this brief but excellent post!

  2. I recently saw SLS in the ingredient list of a rinse out conditioner. Yes, conditioner. If I find it again, I will let you know which it was. In your opinion, what is the point of putting SLS in a conditioner???

    1. used as an emulsifier and thickener

  3. Yep sunsail, I wonder if that is ORS hair mayo? I personally do not see the point or use of SLS in a hair conditioner. It is best left for shampoo.

  4. More than welcome Malinda :)

  5. It was certainly interesting for me to read the article. Thank you for it. I like such topics and anything that is connected to this matter.

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  6. what about baking soda?


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